1. Field of the Invention
The present invention relates to thin-film magnetic heads for use in magnetic disc apparatuses, magnetic tape apparatuses, and the like for recording information on magnetic recording media by a perpendicular magnetic recording method.
2. Description of the Related Art
FIGS. 17 to 24 are views for illustrating conventional thin-film magnetic heads for perpendicular magnetic recording. As shown in FIG. 17, a thin-film magnetic head 31 for perpendicular magnetic recording has a structure in which a nonmagnetic layer 33 composed of Al2O3 and a thick magnetic layer 34 composed of a soft magnetic material such as a Fexe2x80x94Ni-based alloy (permalloy) are formed on a substrate 32 composed of a nonmagnetic material such as an Al2O3xe2x80x94TiC ceramic. A thin magnetic layer 35 composed of a soft magnetic material such as a Fexe2x80x94Ni-based alloy is formed on the nonmagnetic layer 33 and the thick magnetic layer 34. An insulating layer 36 composed of an inorganic insulating material and a conductive coil layer 37 in a spiral shape composed of a low-resistance conductive material such as Cu are sequentially formed in this order on the thin magnetic layer 35. An insulating layer 38 composed of an inorganic insulating material is formed on the insulating layer 36 so as to cover the conductive coil layer 37, and an auxiliary magnetic pole layer 39, composed of a soft magnetic material such as a Fexe2x80x94Ni alloy, is formed on the insulating layer 38 and is magnetically coupled with the thin magnetic layer 35 at the back end portion thereof.
In addition, the thick magnetic layer 34 and the thin magnetic layer 35 form a main magnetic pole layer 40. The individual front end surfaces of the substrate 32, the nonmagnetic layer 33, the thin magnetic layer 34, the insulating layers 36 and 38, and the auxiliary magnetic pole layer 39 form a medium-opposing surface 41 which opposes a magnetic recording medium 42. As shown in FIG. 18, a narrow width of a front end portion 35a of the thin magnetic layer 35 formed on the nonmagnetic layer 33 has a track width Tw.
As shown in FIG. 17, the magnetic recording medium 42, on which information is recorded by the thin-film magnetic head 31 for perpendicular magnetic recording, has a multilayer structure composed of a substrate 43 and a perpendicular magnetizing layer 45, with a soft magnetic layer 44 having high permeability provided therebetween.
In the structure of the thin-film magnetic head 31 for perpendicular magnetic recording and the magnetic recording medium 42 shown in FIG. 17, when a recording current is applied to the conductive coil layer 37, magnetic flux is generated in accordance with the recording current, and the magnetic flux flows in a magnetic circuit formed of the auxiliary magnetic pole layer 39, the main magnetic pole layer 40, the perpendicular magnetizing layer 45, and the soft magnetic layer 44 having high permeability. This magnetizes the perpendicular magnetizing layer 45 of the magnetic recording medium 42 at a part thereof opposing the end surface of the thin magnetic layer 35 of the main magnetic pole layer 40, whereby information is recorded on the magnetic recording medium 42.
The thin-film magnetic head 31 for perpendicular magnetic recording is manufactured by, as shown in FIG. 19, first forming the thick magnetic layer 34 by electroplating on the substrate 32 other than an area from the edge to a slightly inner side thereof, and, as shown in FIG. 20, then forming the nonmagnetic layer 33 on the thick magnetic layer 34 and on the substrate 32 at which the thick magnetic layer 34 is not formed. Subsequently, as shown in FIG. 21, the nonmagnetic layer 33 and the thick magnetic layer 34 are polished by a chemical mechanical polishing method (hereinafter referred to as a CMP method) so that the nonmagnetic layer 33 and the thick magnetic layer 34 have the same thickness.
Next, as shown in FIG. 22, on the nonmagnetic layer 33 and the thick magnetic layer 34, the thin magnetic layer 35 is formed by sputtering, and as shown in FIG. 23, the insulating layer 36 is then formed on the thin magnetic layer 35. On the insulating layer 36, an underlying layer for plating (not shown) and a resist layer 46 are sequentially formed. Subsequently, a pattern 46a corresponding to the conductive coil layer 37 is formed in the resist layer 46 by a photolithographic technique, and electroplating is then performed thereon to thereby form the conductive coil layer 37 on the insulating layer 36.
Next, as shown in FIG. 24, the resist layer 46 and the underlying layer for plating are removed. The insulating layer 38 is then formed on the insulating layer 36 so as to cover the conductive coil layer 37, and the auxiliary magnetic pole layer 39 is formed on the insulating layer 38 by using an electroplating method and a photolithographic technique, whereby the thin-film magnetic head 31 for perpendicular magnetic recording is formed.
In the conventional thin-film magnetic head 31 for perpendicular magnetic recording described above, the insulating layer 36 must be formed flat before the conductive coil layer 37 is formed by a photolithographic technique. The nonmagnetic layer 33 and the thick magnetic layer 34, whose shapes influence the shape of the insulating layer 36, are therefore planarized by polishing using a CMP method. However, due to variations in machining accuracy, the thick magnetic layer 34 constituting the main magnetic pole layer 40 may be polished by more than a predetermined amount. As a result, when a recording current is applied to the conductive coil layer 37, the main magnetic pole layer 40 may be placed in a state of magnetic flux saturation, thereby decreasing the amount of magnetic flux concentrated on the front end portion 35a of the thin magnetic layer 35 constituting the main magnetic pole layer 40. As a result, a problem may arise in that information cannot be recorded on the magnetic recording medium 42.
In addition, and as shown in FIG. 17, since distance A between the conductive coil layer 37 and the front end portion 35a of the main magnetic pole layer 40 is relatively long, it is difficult to ensure sufficient magnetic flux concentrated on the front end surface of the thin magnetic layer 35 of the main magnetic pole layer 40. As a result, a problem may arise in that the magnetic efficiency of the magnetic circuit described above is decreased. The problem described above can be solved by decreasing the distance A and by providing a part of the conductive coil layer 37 on a part of the insulating layer 36 corresponding to the front end portion 35a of the thin magnetic layer 35. However, since the part of the insulating layer 36 mentioned above has a step portion 36a in conformity with the shape of the front end portion 35a of the thin magnetic layer 35, when the pattern 46a is formed in the resist layer 46 by a photolithographic technique, light exposing the resist layer 46 reflects diffusely at the step portion 36a, and the pattern 46a is distorted, whereby the cross-sectional shape and the intervals of the conductive coil layer 37 are damaged. As a result, the characteristics of information recording on the magnetic recording medium 42 are adversely influenced.
The present invention was made in view of the problems of the conventional thin-film magnetic heads described above. An object of the present invention is to provide a thin-film magnetic head for perpendicular magnetic recording, which can concentrate sufficient magnetic flux for recording on an front end portion of a main magnetic pole layer when recording is performed, and which has a magnetic circuit having superior magnetic efficiency.
To these ends, a thin-film magnetic head for perpendicular magnetic recording of the present invention comprises an auxiliary magnetic pole layer having a front end portion opposing a magnetic recording medium; a main magnetic pole layer having a front end portion opposing the front end portion of the auxiliary magnetic pole layer with a spacing therebetween and having a back end portion magnetically coupled therewith so as to form a magnetic circuit together with the auxiliary magnetic pole layer; a conductive coil layer formed in a spiral shape; and insulating layers electrically insulating the auxiliary magnetic pole layer and the main magnetic pole layer from the conductive coil layer; wherein at least one of the insulating layers has a flat surface, the front end portion of the main magnetic pole layer is provided on the flat surface, and a part of the conductive coil layer is disposed between the front end portion of the main magnetic pole layer and the auxiliary magnetic pole layer.
In the structure described above, the main magnetic pole layer comprises a narrow front magnetic pole member forming the front end portion; and a yoke member in contact with a back end part of the front magnetic pole member, the yoke member having a width larger than that of the front magnetic pole member; wherein a back end part of the yoke member is magnetically coupled with the auxiliary magnetic pole layer.
In addition, in the structure described above, the thin-film magnetic head further comprises a coupling magnetic layer formed on the auxiliary magnetic pole layer, wherein the back end part of the yoke member is formed on an upper surface, which is flush with the flat surface of the coupling magnetic layer, and the main magnetic pole layer is magnetically coupled with the auxiliary magnetic pole layer by the coupling magnetic layer.
Furthermore, in the structure described above, at least one of the insulating layers comprises a first insulating layer having the flat surface, and a second insulating layer provided on the flat surface of the first insulating layer. The conductive coil layer comprises a first coil member penetrating the first insulating layer, and a second coil member, which is formed on the flat surface and is connected to a wire extending from the center of the first coil member, penetrating the second insulating layer.
In addition, in the structure described above, the auxiliary magnetic pole layer is also used as an upper shield layer of a magnetoresistive head for reproducing information from the magnetic recording medium.